Performance and uses of expansion agents

1. The magnesium oxide content in the expansion agent shall not exceed 5% (except for the magnesium-containing expansion agents currently on trial). The later expansion of magnesium will cause the hardened concrete structure to crack. The most important physical properties are that the expansion at 7 days of age should not be less than 0.025% and the shrinkage rate (i.e. negative expansion) of 7 days in…